Process of recovering resinous by-products in the manufacture of wood pulp



E. H. FRENCH PROCESS OF RECOVERINC- RESINOUS BY PRODUCTS June 15, W31.

IN THE MANUFACTURE OF WOOD PULP Original Filed Aug. 15. 1925 2Sheets-Sheet 1 June 16, 1931. E. H. FRENCH 1,810,472 PROCESS OFREQOVERING RESINOUS BY-PRODUCTS' IN THE MANUFACTURE OF WOOD PULPOriginal Filed Aug. 15, 1925 2 Sheets-Sheet 2 [raven/tor Patented June16, 1931 UNITED STATES- PATENT; OFFICE I E. FRENCH, OF COLUMBUS, OHIOrnocnss or nncovanme nnsmous nY-rnonucrs in THE mnrnc'runn 01' ,woonroar Original application ined August 115, i985, Serial No. 50,526.Divided and this application nied October 29,

1928. Serial No. 315,784.

In the manufacture of paper pulp produced from resinous woods by theso-called sul-' phate process the wood is cleaned and chipped, placed ina digester where it is treated' with a solution containing sodiumsulphid (Na S) and caustic soda, the wood being cooked with steam underpressure in this liquor'for a period of several hours. The turpentine ofthe mass is recovered by distillation and the digester is blown, thepulp separated "from the pulping liquor sometimes called black liquor),and the latter is evaporated to a thin paste, and burned in a furnacefor the purpose of consumin the 16 organic matter and converting thesulp ates in the mass to sulphids and carbonates.

During the cooking of the wood, the pulping liquor (black liquor)acquiresa large quantity of resinous substances such as rosm and rosinoils in the form principally of sodium resinate as the result of thecombination of the caustic soda with the abietic acid of the rosin ofthe wood. Many attempts have been made to recover the sodium resinatesbut, as far as I am aware, without commercially satisfactory results.'Among line liquors oontainin has had' value onlyas fuel for firing theblack ash furnace used to'decompose the sodium sulphateinto sodiumcarbonate and sodium sulphid.

The object of this invention therefore is to'provide an improved andeconomic method of recovering the resinous content of alkaresinates,such as pulping liquor, especial y that resulting from the sulphate orsoda process of paper manufacture, in a form and quality equahfng,

if not superior to that obtained directly from the crude resin Myinvention is particularly effective in treating the liquor obtained fromthe stumpageof the long-leaf pine which contains400to 700 pounds ofrosin to the cord, but its employment is profitable in the treatment ofliquors" obtained from the pulping of woods having a smaller content 0rosin.

The chemical formula of the abietieacid is given by some authorities asC H O and byothers as (3 K 0, thus signifying a molecular weight ofapproximately 302 and 288 respectively. p v y a In the sulphate processof manufacturing pulp the alkali employed is usuall derived from saltcake (1m ur e sodium phate) which after passing roughthe black ashfurnace is changed, in the presence of organic matter therein, tosodiumcarbonate and sodium sulphid as already indicated. Therefore assuming,as an example, that the rosin content of a cord of wood is 500'pounds,-there will be required about to pounds of salt cake to produce theamount of sodium hydroxide or sul'hid necessa to neutralize the abieticacid content 0 the resinous matter of the wood. The sodium resinatecontained in the spent pulping liquor is soluble in the latter.

In carrying out my process I add 'suilicient nitre cake (impure sodiumacid sulphate) to the black liquor above-referred to so as toprecipitate all of the sodium resinate in the form of rosin, thisreaction being accompanied by released and precipitated ligneous acids.Nitre cake is consi ered herein on account of its renounced acidproperties as constitut' or present purposes an acid. Simultaneo wit theprecipitation of the rosin the com ined sodiumof the resinate and of theorganic acids present which have been derived fromthe wood pulp,'suchasformic and acetic acids, unite with the sulphate ions of the nitre caketo formsulphates which in passing through the'standard black ash furnaceare-again converted into sodium sulphid and sodium carbonate, both ofwhich may be used in the ulping process. There thus results anadditional quantity of sodium sulphate due to the use of the nitre cake,

such additional quantity amounting to about 50% of the nitre cakeemployed. By my process, therefore, I simultaneously secure two valuableresults, namely, the recovery of rosin from the spent pulping liquor,and the recovery of the sodium sulphate at a very low cost. The amountof nitre cake needed for complete precipitation of the resins should bedetermined in each batch of spent liquor by analyzing it for alkalinityand sodium resinate content by the standard methods of analysis, becausethe resinous content of wood varies according to the var1ety of woodused as well as according to the part of the tree from which it comes.

In the black ash furnace above mentioned, WhlCh is used for the purposeof converting the impure sodium sul hate into sodium sulphid and sodiumcar onate, the reactions taking place form gases containing sulphurdioxide which go into the atmosphere as ob- ]ectionable fumes. Shouldnitre' cake be unavailable for economic reasons, I pass the gases formedin the black ash furnace through the blackliquor which serve all of thefunctions of the more expensive sulphuric acid, the sulphur dioxideformed when the sodium sulphateis heated sufiiciently. in the presenceof organic matter uniting with the Water present to form sulphurous acidwhich preclpitates the rosin from the sodium resmate in the same manneras when nitre cake or sulphuric acid is used. This procedure not onlyeffects the precipitation of the rosin and any accompanyingwater-insoluble organlc acids and ligneous impurities, but it eliminatesat the sameltime the objectionable fumes mentioned above.

In the accompanying drawings:

Figure 1 is a plan view of the apparatus Employed in carrying out thepresent inven- Figure 2 is a side elevation thereof; and v Figure 3 is avertical sectional view'of the tankemployed in the separa ion of therosin from the black liquor. j j

One convenient method for carrying out the first step of my process,that is the conversion of the soluble sodium resinate in the blackliquor into rosin, is shown in the accompanying drawings, in Figure 1 ofwhich A, A, and A" are .tanks in which black liquor is treated for thepurpose of liberating rosin from the sodium resinate. Figure 3 shows across-section of one of the above-mentioned tanks. At the upper part ofeach of the tanks is a circular trough or colander having the upper partperforated, and within these colanders are the steam coils 5. Eachcolander is providediwith a rosin outlet trough 6. Suspended in thecenter of the top: of the respective tanks A, A" and A" are the conicaldeflectors 7. Imme- 65 diately below the colander is the black liquoroutlet 8, having the regulating valve 9 therein. Near the bottom of eachof these tanks is a perforated coil 10.

To carry out the first step of the operation, the black li nor is fedinto the tank A through the eed-line 1, the flow being regulated by thevalve 2. After the tank has been filled to a point above the outlet 8,the valve 9 is regulated so that the height of the liquor is below theopening in the side'of the colan-. der. v Acid preferably in gaseousform such as the acid. gas from the black ash furnace described above,and which contains sulphur. dioxide, or as obtained from any othersuitable source, is pumped through the perforated coil 10 into the tankwhere it reacts with the sodium resinate to liberate rosin, the latterof which is carried to the surface of the li nor with the=excess of thegases introduced into the tank, substantially as fast as the former isformed.

The next step in my process is to separate the precipitate from teliquor; This is done by decantation or by filteringthe mixture. Thedecantation is aided by the conical de-. flector 7 shown in Figure 3,the impure rosin being carried into the trough 6 by means of thecolander heated by the steam coils 5, and from there into the solventtanks B and B. The precipitate, which contains many impurities such asvarious organic aclds and other ligneous matter, is then digested atatmospheric pressure with an organic solvent such as benzol, gasoline,toluol, or kerosene in quantity sufficient to dissolve the-rosin and Irosin oils. The dissolving of the rosin and rosin oils can be carriedout at ordinary atmospheric temperatures by means of the agitator 12,(Figure 1). After the solution has been accomplished, the liquid isready for 1' distillation. e

This solution of resinous matter. resulting from the above-mentioneddigestion is dzhen distilled under a. reduced pressure, and when thisdistillation is carried out in a glass ap- 11o paratus with about 4 emsof mercury pressure it can be distilled over with the rosinpracticallyundecomposed,but in iron stills it is difiicult to prevent somedecomposition of the rosin into a hydrocarbon variously known as Illcolophene or abietene which is produced upon the elimination of thecarboxyl group from the rosin acid.

Because of the decomposition which takes place when the pressure isincreased or in the presence of metals, it is' advisable in thedistillation in a metallic still to further reduce the boiling point ofthe rosin by first preheating the solution of rosin and atomizing themixture by means of pressure on the liquid, 2

forcing it through a spray or atomizing nozzle into a vacuumizedchamber, and condensing fractionally both the organic solvent and therosin contained therein, the vapor from the organic solvent thus servingsufliciently By referring to F lgures 1 and 2 of the drawings the mannerof carrying out the above step will be understood. The solution of resinin gasoline in the solvent tanks B and B is forced by the pump 13through the'line 15 to the preheater 29 where it is heated to the propertemperature, and from thence is forced to the pressure tank 16. Here apressure sufliciently high to atomize the rosm as it flows into thestills D, D and D", is maintained. The respective stills D, D, and D"have connected therewith the condensers E,

connections leading to the respective dist/ll.- late receivin tanks F toF. A high vacuum is maintained upon the various st1lls and condcnsers bvthe vacuum pump 17 which is contillation is nected to the line throughcondenser G.

\Vhere the final product desired is rosin, the condensers E, E, and E"are maintained sufliciently hot by the control of the cooling waterthereto to maintain the solvent in the gaseous form but sufiicientlycool to condense the resin. The steam coil 18 is provided for thepurpose of maintaining the receiving tanks F to F at a temperature toprevent the condensation of the solvent which therefore passes to thecondenser d and is there condensed and tapped off for reuse in theprocess. The rosin is drawn off through the valve 26. I I

For atomizing the rosin-solvent solution into the stills, atomizingpressures will vary, depending upon such factors as the type of nozzleused, the volume of solution to be sprayed in a, given time, and thelike. The said pressures usually range from ten pounds per sq. in. uward. The temperature of disthe kind of solvent use and the degree ofvacuum obtainable. Where a'good grade of kerosene is used, and anabsolute pressure of about 4 cm. of mercury is obtainable on the stillthetemperature of the liquid in the still will range around 240.0.,providing two parts of the solvent are used to one part of the rosin.

It is well known that from 35% to 40% of the rosin produced in thiscountry enters into the manufacture of resin soap, and for this purposethe resin acids are neutralized or saponified with soda ash or causticsoda. I

have discovered that the rosin in the organic solution aforementionedeither before or after distillation may be recovered from the solutionby adding an aqueous solution of an alkali to the resin solution andagitating the mixture thereby neutralizing the ependent u onsuch factorsas ,the floating of t surface of the liquor is effectedsubstantialabietic acid which will separate out first as an emulsion butlater on standin it will break down so that it will be in so ution inthe water, thus being separated from the organic solvent which willforma distinct layer on the top that can be decanted to be again used todissolve succeedingbatches. The solution of sodium resinate- 1n water isthen evaporated, leaving the granular sodium resinate as a residueuseful in manufacturing soap or paper size.

When sodium resinate is to be manufactured, the entire distillate iscondensed in the condensers E, E, and E, and collected in the receivintanks F to F. The resultant condensate 1s forced bymeans of pump 23 tothe tank H in which the rosin is converted to sodium resinate by meansof caustic soda 'or the like. The tank H is equipped with E, and E", andthe latter have liquid drairf,

means for agitating the liquid during the neutralization step, anditalso has connected thereto the condenser I and the pump 25, the

procedure involved in the resinateproduction being. disclosed andclaimed in m copendipg application No. 172,821, filed arch 4,192 x Thisapplication is a division of my copending application No. 50,526, filedAugust 15, 1925, now matured into Patent #1,693,586 issued Nov. 27,1928.

My invention is susceptible of modification within the scope of theappended claims;

I claim:

1. The process of recovering rosin from alkaline liquors containingresinates which comprises the ste of passing an acid gas through thesaid liquors to liberate at least part of the rosin content thereof.

2. The process of recovering resin from al-- kallne liquors containingresmates which comprises adding an acid material to the liquor in anamount sufiicient to decompose which an acid gas is used both todecompose the resinates and to float the thus-formed resin to thesurface of the liquor.

4. The rocess'as defined in claim-2 in which the ec'omposition of the.resinates and e thus-formed resin to the ly simultaneously. v

5. The process as defined in claim 2. in

which sulphur dioxide gas is used both todecompose the resinates and tofloat the resin to the surface of the liquor.

the liquor by means of waste gases obtained from the combustion of blackash.

7. The process of recovering rosin from alkaline liquors containingresinates which 6; The process as. defined in claim 2 in comprises thestep of passing sulphur dioxide-containing gases through the saidliquors to liberate at least part of the rosin content therein.

8. In theprocess of recovering rosin from alkaline pulping liquorscontaining resinates, the step of passing therethrough the combustiongases from the calcination of black ash.

9. In the process of recovering rosin from alkaline liquors containingresinates, the

steps of passing an acid gas through an alkaline solution of theresinates in amount suflicient to liberate at least part of the rosincontained therein, floating the liberated rosin to the surface of theliquor,- and decanting the rosin from the liquor.

10. The process of recovering rosin from alkaline resinate solutionswhich comprises the step of passing an acid gas through the saidsolution in amount suflicient to neutralize at least a part of theresinates coniained therein to form rosin, and floating the rosin to thesurface of the solution.

In witness whereof I have hereunto set my hand this 27th day of October,1928.

EDWARD H. FRENCH.

